Field of the Invention
The present invention relates generally to check valves and, more specifically, to an improvement over check valves with no external moving parts which can be used to indicate a position of an internal valve disc.
Check valves having a closure mechanism consisting of a disc have been commonly used in fluid handling systems to prevent reverse flow in such systems for many years. Typically, these disc check valves have a disc that rotates within the valve body. The disc includes a hinge which is fully contained in the valve body or the valve disc which reduces the possibility of valve body leakage, but prevents indication of disc position. An example of these types of valves is shown in U.S. Pat. No. 4,054,153 and U.S. Pat. No. 5,341,840. The disc typically pivots between about 35.degree.-90.degree. to an open position thereby providing a full flow area or near full flow area. The 35.degree. span of movement is preferred because it provides a short closing stroke which avoids a slamming of the valve in a closed position. The above-described design is reliable because there is only one moving part--the disc. Further, the integral connection between the hinge and the disc avoids any penetrations of the disc for a connection between the hinge and the disc.
While the standard disc check valve design is reliable and economical, many check valve users desire an indication of the position of the disc to verify that there is forward flow in the pipeline containing the check valve. Lack of forward flow may be an indication of pump failure, line blockage, or loss of prime. If the valve remains closed with the pump running and no flow, serious damage to the pump or piping system may occur. Because of this risk, users find it necessary to use more expensive and complex check valves with external levers or spring mechanisms. An example of this type of indicating valve mechanism is disclosed in U.S. Pat. No. 5,746,246.